JP5778284B2 - Imaging lens and imaging apparatus using the same - Google Patents

Description

  The present invention relates to an imaging lens and an imaging apparatus, and more particularly to a monitoring camera, a portable terminal camera, an in-vehicle camera, and the like using an imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). The present invention relates to an imaging lens used and an imaging device using the imaging lens.

  2. Description of the Related Art In recent years, there have been known image pickup elements such as CCDs and CMOSs that are extremely downsized and have high pixels. At the same time, the image pickup apparatus body provided with these image pickup elements is also miniaturized, and an image pickup lens mounted on the image pickup apparatus is used in addition to good optical performance. On the other hand, even for applications such as surveillance cameras and in-vehicle cameras that are imaging devices, there are known lenses equipped with a small and high-performance imaging lens while being a wide-angle lens.

  As imaging lenses having a relatively small number of lenses in the above fields, for example, imaging lenses described in Patent Documents 1 to 4 below are known.

JP-A-1-134324 Japanese Patent Laid-Open No. 7-253542 JP 2001-356265 A JP 2010-191019 A

  However, the imaging lens described in Patent Document 1 is difficult to correct aberrations because the position of the stop is located further on the image side than the most image side lens surface constituting the imaging lens. In addition, when the imaging lens of Patent Document 1 has a brightness of about F4.0, it can be said that the imaging lens has a configuration capable of correcting aberrations. There arises a problem that the outer diameter of the lens closest to the object becomes very large. In the imaging lens of Example 3 described in Patent Document 1, the convex lens as the second lens is already in a state where there is no room in the size of the lens outer diameter, so that it can cope with a bright imaging lens. It is hard to think that it was composed.

  Further, the imaging lens of Example 2 described in Patent Document 2 is as dark as F4, and further has large chromatic aberration and astigmatism, so that it is unsuitable for use in an imaging apparatus with advanced image quality.

  The imaging lens of Example 5 described in Patent Document 3 is also dark at F3.6, and also has large chromatic aberration and astigmatism. Therefore, the imaging lens is inappropriate for use in an imaging apparatus with improved image quality. is there.

  In addition, the imaging lens of Example 5 described in Patent Document 4 is dark as F3.25, and also has large chromatic aberration, astigmatism, and distortion aberration. Therefore, it is not suitable for use in an imaging apparatus that requires high image quality. It is inappropriate.

  Due to the above, there is a demand to use an imaging lens that is bright at about F2.2, particularly has good optical performance that is well corrected for axial chromatic aberration and can respond to an increase in the number of pixels of the imaging device. .

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a bright and wide-angle and compact imaging lens in which various aberrations are well corrected, and an imaging apparatus using the imaging lens. It is.

First imaging lens of the present invention includes, in order from the object side, a negative first lens group and a positive second lens group, the first lens unit includes only a first lens which is a single double-concave lens The second lens group includes, in order from the object side, a cemented lens having a positive refractive power as a whole by cementing a second lens that is a positive lens and a third lens that is a negative lens in this order from the object side. It consists of a diaphragm, a fourth lens that is a positive lens, and a fifth lens that is a negative lens. Conditional expression (1a): 0 <f23 / f <2.5, conditional expression (2a): 0 <f45 / f <6 is satisfied at the same time. Here, f23 is a combined focal length of the second lens and the third lens, f45 is a combined focal length of the fourth lens and the fifth lens, and f is a focal length of the entire lens system.

  The first imaging lens preferably satisfies the conditional expression (1a ′): 0.6 <f23 / f <2, and the conditional expression (1a ″): 1 <f23 / f <1.8 is satisfied. It is more preferable that the first imaging lens satisfies the conditional expression (2a ′): 0.5 <f45 / f <5.5, and the conditional expression (2a ″): 2 It is more desirable to satisfy <f45 / f <5.

Second imaging lens of the present invention includes, in order from the object side, a negative first lens group and a positive second lens group, the first lens unit includes only a first lens which is a single negative lens The second lens group includes, in order from the object side, a cemented lens having a positive refractive power as a whole by cementing a second lens that is a positive lens and a third lens that is a negative lens in this order from the object side. It consists of a stop, a fourth lens that is a positive lens, and a fifth lens that is a negative lens. Conditional expression (1b): 0.9 <f23 / f <2.4, conditional expression (2b): 2.8 <F45 / f <6 is satisfied at the same time. Here, f23 is a combined focal length of the second lens and the third lens, f45 is a combined focal length of the fourth lens and the fifth lens, and f is a focal length of the entire lens system.

  The second imaging lens preferably satisfies conditional expression (1b ′): 1 <f23 / f <2, and conditional expression (1b ″): 1.1 <f23 / f <1.6 is satisfied. It is more preferable that the second imaging lens satisfies the conditional expression (2b ′): 2.9 <f45 / f <5, and the conditional expression (2b ″): 3 <f45. It is more desirable to satisfy /f<4.2.

The third imaging lens of the present invention includes, in order from the object side, a negative first lens group and a positive second lens group, the first lens unit includes only a first lens which is a single negative lens The second lens group includes, in order from the object side, a cemented lens having a positive refractive power as a whole by cementing a second lens that is a positive lens and a third lens that is a negative lens in this order from the object side. Conditional expression (3a): 0 is composed of a stop, a cemented lens having a positive refractive power as a whole by cementing a fourth lens as a positive lens and a fifth lens as a negative lens in this order from the object side. .9 <fg2 / f <1.8 is satisfied. Here, fg2 is the focal length of the second lens group (the combined focal length of the second lens to the fifth lens), and f is the focal length of the entire lens system.

  The third imaging lens preferably satisfies conditional expression (3a ′): 1 <fg2 / f <1.6, and conditional expression (3a ″): 1.05 <fg2 / f <1. It is more desirable to satisfy 4.

  The first lens in the second and third imaging lenses can be a biconcave lens.

  In the second and third imaging lenses, the second lens is a biconvex lens, the third lens is a negative lens with a concave surface facing the object side, the fourth lens is a biconvex lens, and the fifth lens is concave on the object side. Can be a negative lens.

  The third lens in the second and third imaging lenses may have a meniscus shape.

  The fifth lens in the second and third imaging lenses may have a meniscus shape.

  The second and third imaging lenses may form a cemented lens having a positive refractive power as a whole in which the fourth lens and the fifth lens are cemented with each other.

  The first and second imaging lenses can satisfy the conditional expression (3b): 0.5 <fg2 / f <2.5. Here, fg2 is the focal length of the second lens group (the combined focal length of the second lens to the fifth lens), and f is the focal length of the entire lens system. The first and second imaging lenses preferably satisfy the conditional expression (3b ′): 0.9 <fg2 / f <1.8, and the conditional expression (3b ″): 1 <fg2 / f <. It is more desirable to satisfy 1.3.

  The first to third imaging lenses may satisfy the conditional expression (4): −2 <f1 / fg2 <0. Here, f1 is the focal length of the first lens, and fg2 is the focal length of the second lens group (the combined focal length of the second lens to the fifth lens). The first to third imaging lenses preferably satisfy the conditional expression (4 ′): − 1 <f1 / fg2 <−0.5, and the conditional expression (4 ″): −0.9 <f1. It is more desirable to satisfy /fg2<−0.6.

  The first to third imaging lenses may satisfy the conditional expression (5): 1.5 <(dsi) / f <3.2. Here, dsi is the distance between the stop and the image plane on the optical axis (the back focus portion is an air conversion distance), and f is the focal length of the entire lens system. The first to third imaging lenses preferably satisfy the conditional expression (5 ′): 1.8 <(dsi) / f <2.8, and the conditional expression (5 ″): 2 <(dsi ) / F <2.5 is more preferable.

  The first to third imaging lenses may satisfy the conditional expression (6): 0.42 <(dsi) / L <1. However, dsi is the distance between the stop and the image plane on the optical axis (the back focus portion is the air conversion distance), and L is the total optical length. The first to third imaging lenses preferably satisfy the conditional expression (6 ′): 0.45 <(dsi) / L <0.9, and the conditional expression (6 ″): 0.48 <. It is more desirable to satisfy (dsi) / L <0.8.

  An imaging apparatus according to the present invention includes any one of the first to third imaging lenses.

  The negative first lens group means a first lens group having negative refractive power, the positive second lens group means a second lens group having positive refractive power, and the negative lens is A lens having a negative refractive power is meant, and a positive lens means a lens having a positive refractive power.

  The first to third imaging lenses can be substantially composed of two lens groups. Note that “substantially composed of two lens groups” means a lens having substantially no refractive power, an optical element other than a lens such as a diaphragm or a cover glass, a lens flange, etc., in addition to the two lens groups. , An imaging lens having a lens barrel, an imaging device, a mechanism portion such as a camera shake correction mechanism, and the like.

  The air-converted back focus is a distance (air-converted distance) on the optical axis from the most image-side lens surface of the imaging lens to the image-side imaging surface (imaging surface) of the imaging lens. This air-converted back focus is obtained when an optical element having no refractive power, such as a filter or a cover glass, is disposed between the lens surface closest to the image side and the imaging surface. The thickness is determined in terms of air.

  dsi is the distance between the stop and the imaging surface, and the actual length is used for the distance between the apex of the most image side lens surface and the stop in the imaging lens, and the apex of the most image side lens surface and the image forming surface Is an air conversion interval, that is, an interval determined using an air conversion back focus.

  The air conversion interval is determined by converting the thickness of these optical elements into air when optical elements having no refractive power such as a filter and a cover glass are arranged in the interval. If no optical element having no refractive power is arranged in the interval, the interval is simply an air interval.

  The optical total length TL is a distance on the optical axis from the most object-side lens surface of the imaging lens to the image-side imaging surface (imaging surface) of the imaging lens. This distance is the distance from the most object-side lens surface constituting the imaging lens to the most image-side lens surface using an actual length that is not converted to air, and the distance from the most image-side lens surface to the imaging surface. Is determined using an air equivalent back focus.

  When an aspherical surface is used for the imaging lens, the aspherical irregularity, the aspherical refractive power positive / negative, and the aspherical curvature radius positive / negative are the aspherical paraxial region irregularity, refractive power positive / negative, and It shall be defined by the sign of the radius of curvature.

  According to the first imaging lens and the imaging apparatus of the present invention, the negative lens group and the positive second lens group are arranged in order from the object side, and the first lens group is a single biconcave lens. It consists only of the first lens, and the second lens group is joined in order from the object side, and the second lens that is a positive lens and the third lens that is a negative lens are joined in this order from the object side. It is assumed that the lens includes a cemented lens having power, a stop, a fourth lens that is a positive lens, and a fifth lens that is a negative lens. Conditional expression (1a): 0 <f23 / f <2.5, conditional expression (2a): Since 0 <f45 / f <6 is satisfied at the same time, various aberrations can be satisfactorily corrected while being bright and having a wide angle of view and compactness.

  According to the second image pickup lens and the image pickup apparatus of the present invention, the negative first lens group and the positive second lens group are provided in order from the object side, and the first lens group is a single negative lens. It consists only of the first lens, and the second lens group is joined in order from the object side, and the second lens that is a positive lens and the third lens that is a negative lens are joined in this order from the object side. It is assumed that the lens includes a cemented lens having power, a stop, a fourth lens that is a positive lens, and a fifth lens that is a negative lens. Conditional expression (1b): 0.9 <f23 / f <2.4, Conditional expression (2b): Since 2.8 <f45 / f <6 is satisfied at the same time, various aberrations can be corrected satisfactorily while being bright and having a wide angle of view.

  According to the third imaging lens and imaging apparatus of the present invention, the negative lens group and the positive second lens group are arranged in order from the object side, and the first lens group is a single negative lens. It consists only of the first lens, and the second lens group is joined in order from the object side, and the second lens that is a positive lens and the third lens that is a negative lens are joined in this order from the object side. A cemented lens having a power, a stop, and a cemented lens having a positive refractive power as a whole by cementing a fourth lens as a positive lens and a fifth lens as a negative lens in this order from the object side Since conditional expression (3a): 0.9 <fg2 / f <1.8 is satisfied, various aberrations can be corrected satisfactorily while being bright and having a wide field angle.

  The operation and effect of each conditional expression will be described later.

Sectional drawing which shows schematic structure of the imaging lens and imaging device by embodiment of this invention Sectional drawing which shows schematic structure of the imaging lens of Example 1. FIG. Sectional drawing which shows schematic structure of the imaging lens of Example 2. Sectional drawing which shows schematic structure of the imaging lens of Example 3. Sectional drawing which shows schematic structure of the imaging lens of Example 4. Sectional drawing which shows schematic structure of the imaging lens of Example 5. (A) to (d) are aberration diagrams of the imaging lens of Example 1. (A) to (d) are aberration diagrams of the imaging lens of Example 2. (A)-(d) are aberration diagrams of the imaging lens of Example 3. (A) to (d) are aberration diagrams of the imaging lens of Example 4. (A) to (d) are aberration diagrams of the imaging lens of Example 5. The figure which shows the camera for surveillance which mounts the imaging lens of this invention

  Hereinafter, an imaging lens according to an embodiment of the present invention and an imaging apparatus using the imaging lens will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a schematic configuration of an imaging apparatus using an imaging lens according to an embodiment of the present invention, together with an optical path of a light beam passing through the imaging lens. Note that arrows X, Y, and Z in FIG. 1 indicate three directions that are orthogonal to each other, similarly to arrows X, Y, and Z in FIGS. 2 to 6 described later, and the direction of the arrow Z indicates the optical axis Z1. Indicates the same direction.

  An imaging lens 100 illustrated in FIG. 1 shows three types of embodiments in common, the imaging lens 101 according to the first embodiment of the present invention to the imaging lens 103 according to the third embodiment. Similarly, the image pickup apparatus 200 illustrated in FIG. 1 includes the image pickup lenses 101 to 103, and the image pickup apparatus 201 according to the first embodiment and the image pickup apparatus 203 according to the third embodiment of the present invention. Three types of embodiments are shown in common.

  As described above, the imaging lenses 101 to 103 are collectively referred to as the imaging lens 100. The imaging devices 201 to 203 are collectively referred to as the imaging device 200.

  The illustrated imaging apparatus 200 includes an imaging element 210 that is a solid-state imaging element such as a CCD or CMOS, and a single-focus imaging lens 100. For example, a digital camera, a mobile terminal camera, a monitoring camera, an in-vehicle camera, It is used for a reading camera for the purpose of detecting a defect or identifying an individual.

  The imaging element 210 converts an optical image Im representing the subject 1 imaged on the light receiving surface 210J of the imaging element 210 through the imaging lens 100 into an electrical signal, and outputs an image signal Gs indicating the optical image Im. Is. Note that the imaging apparatus 200 is configured such that the imaging plane Km formed by the imaging lens 100 is positioned on the light receiving surface 210J of the imaging element 210.

  The imaging lens 100 includes a negative first lens group G1 and a positive second lens group G2 in order from the object side. The first lens group G1 includes only the first lens L1, which is a single negative lens. The second lens group G2 is a cemented lens having a positive refractive power as a whole by cementing a second lens L2 that is a positive lens and a third lens L3 that is a negative lens in this order from the object side. And an aperture stop St, a fourth lens L4 that is a positive lens, and a fifth lens L5 that is a negative lens. The above configuration is common to the imaging lenses 101 to 103.

  As described above, the imaging lens 100 includes, in order from the object side, the negative first lens L1, the positive second lens L2, the negative third lens L3, the aperture stop St, the positive fourth lens L4, and the negative fifth lens. A lens L5 is provided.

  The imaging lens 101 further makes the first lens L1 a biconvex lens, and simultaneously satisfies the conditional expression (1a): 0 <f23 / f <2.5 and the conditional expression (2a): 0 <f45 / f <6. It is comprised so that it may do.

  The imaging lens 101 preferably satisfies the conditional expression (1a ′): 0.6 <f23 / f <2, and satisfies the conditional expression (1a ″): 1 <f23 / f <1.8. The imaging lens 101 preferably satisfies the conditional expression (2a ′): 0.5 <f45 / f <5.5, and the conditional expression (2a ″): 2 <f45 / f. It is more desirable to satisfy <5.

  The imaging lens 102 is further configured to satisfy the conditional expression (1b): 0.9 <f23 / f <2.4 and the conditional expression (2b): 2.8 <f45 / f <6 at the same time. It is.

  The imaging lens 102 preferably satisfies the conditional expression (1b ′): 1 <f23 / f <2, and satisfies the conditional expression (1b ″): 1.1 <f23 / f <1.6. The imaging lens 102 preferably satisfies the conditional expression (2b ′): 2.9 <f45 / f <5, and the conditional expression (2b ″): 3 <f45 / f <4. .2 is more desirable.

  The imaging lens 103 further forms a cemented lens having a positive refractive power as a whole in which the fourth lens L4 and the fifth lens L5 are cemented with each other, and the conditional expression (3a): 0.9 <fg2 / It is configured to satisfy f <1.8.

  The imaging lens 103 preferably satisfies the conditional expression (3a ′): 1 <fg2 / f <1.6, and the conditional expression (3a ″): 1.05 <fg2 / f <1.4 is satisfied. Satisfaction is more desirable.

  Furthermore, the imaging lens 100 can have the following configuration.

  In the imaging lenses 102 and 103, the first lens L1 can be a biconcave lens.

  In the imaging lenses 102 and 103, the second lens L2 is a biconvex lens, the third lens L3 is a negative lens with a concave surface facing the object side, the fourth lens L4 is a biconvex lens, and the fifth lens L5 is concave on the object side. Can be a negative lens.

  In the imaging lenses 102 and 103, the third lens L3 can be a meniscus lens, or the fifth lens L5 can be a meniscus lens.

  The imaging lenses 102 and 103 can form a cemented lens having a positive refractive power as a whole in which the fourth lens and the fifth lens are cemented with each other.

  The imaging lenses 101 and 102 can satisfy the conditional expression (3b): 0.5 <fg2 / f <2.5. The imaging lenses 101 and 102 preferably satisfy the conditional expression (3b ′): 0.9 <fg2 / f <1.8, and the conditional expression (3b ″): 1 <fg2 / f <1.3. It is more desirable to satisfy.

  The imaging lenses 101 to 103 can satisfy the conditional expression (4): −2 <f1 / fg2 <0. The imaging lenses 101 to 103 preferably satisfy the conditional expression (4 ′): − 1 <f1 / fg2 <−0.5, and the conditional expression (4 ″): −0.9 <f1 / fg2 < It is more desirable to satisfy −0.6.

  The imaging lenses 101 to 103 can satisfy the conditional expression (5): 1.5 <(dsi) / f <3.2. The imaging lenses 101 to 103 preferably satisfy the conditional expression (5 ′): 1.8 <(dsi) / f <2.8, and the conditional expression (5 ″): 2 <(dsi) / f. It is more desirable to satisfy <2.5.

  The imaging lenses 101 to 103 can satisfy the conditional expression (6): 0.42 <(dsi) / L <1. The imaging lenses 101 to 103 preferably satisfy the conditional expression (6 ′): 0.45 <(dsi) / L <0.9, and the conditional expression (6 ″): 0.48 <(dsi). It is more desirable to satisfy /L<0.8.

  The effects of the conditional expressions will be described together below.

[Effects of conditional expression defining the range of f23 / f]
Each of the conditional expressions (1a) and (1b) defines the range of the ratio between the combined focal length f23 of the second lens and the third lens and the focal length f of the entire lens system.

  By configuring the imaging lens and the imaging device so as to satisfy the conditional expression (1a) or (1b), the beam diameter at the point where the height of the axial beam with respect to the optical axis Z1 is the highest in the entire lens system. Various aberrations can be suppressed while suppressing the size (while downsizing).

  If the upper limit of conditional expression (1a) or (1b) is exceeded, the aberration will be good, but the optical total length L will be extended. If an attempt is made to suppress the elongation of the optical total length L, the difference (spherical aberration bulge) between the spherical aberration in the marginal ray and the spherical aberration in the ray passing through a height of about 70% of the marginal ray increases. On the other hand, if the lower limit of conditional expression (1a) or (1b) is not reached, spherical aberration will be undercorrected and spherical aberration will be under (undercorrected).

  The operations and effects of the conditional expressions (1a ′), (1a ″), (1b ′), and (1b ″) are the same as those in the conditional expressions (1a) and (1b).

[Effects of conditional expressions defining the range of f45 / f]
Conditional expressions (2a) and (2b) respectively define the range of the ratio between the combined focal length f45 of the fourth lens and the fifth lens and the focal length f of the entire lens system.

  By configuring the imaging lens and the imaging device so as to satisfy the conditional expression (2a) or (2b), it is possible to balance various aberrations while reducing the size.

  When the upper limit of conditional expression (2a) or (2b) is exceeded, the tangential image plane falls to the under side. On the other hand, if the lower limit of conditional expression (2a) or (2b) is not reached, the spherical aberration falls to the under side.

  The operations and effects of the conditional expressions (2a ′), (2a ″), (2b ′), and (2b ″) are the same as those in the conditional expressions (2a) and (2b).

[Effects of conditional expressions defining the range of fg2 / f]
Each of the conditional expressions (3a) and (3b) indicates the range of the ratio between the focal length of the second lens group G2 (the combined focal length of the second lens L2 to the fifth lens L5) fg2 and the focal length f of the entire lens system It prescribes.

  By configuring the imaging lens and the imaging device so as to satisfy the conditional expression (3a) or (3b), the back focus can be lengthened while achieving compactness.

  When the upper limit of conditional expression (3a) or (3b) is exceeded, the focal length of the second lens group G2 becomes long, so that the optical total length L increases. If it is attempted to suppress the elongation of the optical total length L, as described above, the bulge of spherical aberration increases and performance degradation occurs. On the other hand, if the lower limit of conditional expression (3a) or (3b) is not reached, the optical total length L tends to be shortened, but the spherical aberration falls to the under side, and this spherical aberration becomes insufficiently corrected.

  The operations and effects of the conditional expressions (3a ′), (3a ″), (3b ′), and (3b ″) are the same as those in the conditional expressions (3a) and (3b).

[Effects of conditional expressions defining the range of f1 / fg2]
Conditional expression (4) defines the range of the ratio between the focal length f1 of the first lens group 1G and the focal length fg2 of the second lens group 2G.

  By configuring the imaging lens and the imaging device so as to satisfy the conditional expression (4), it is possible to keep the balance between the spherical surface and the image plane appropriately while achieving compactness.

  If the upper limit of conditional expression (4) is exceeded, it will be easy to ensure a long back focus, but the spherical aberration will be excessive. On the other hand, if the lower limit of conditional expression (4) is not reached, the refractive power of the first lens group 1G becomes weaker than the refractive power of the second lens group 2G, so that the back focus is shortened and the image plane is on the under side. Fall down.

  The operations and effects of the conditional expressions (4 ′) and (4 ″) are the same as those in the conditional expression (4).

[Operational effect of conditional expression defining range of (dsi) / f]
Conditional expression (5) defines the range of the ratio between the distance dsi between the stop St and the imaging plane Km on the optical axis Z1 and the focal length f of the entire lens system.

  By configuring the imaging lens and the imaging device so as to satisfy the conditional expression (5), the imaging lens and the imaging device can be made compact.

  If the upper limit of conditional expression (5) is exceeded, the optical total length L increases. If it is attempted to suppress the elongation of the optical total length L, as described above, the bulge of spherical aberration increases and performance degradation occurs. On the other hand, when the lower limit of conditional expression (5) is not reached, the back focus is shortened.

  The operations and effects of the conditional expressions (5 ′) and (5 ″) are the same as those in the conditional expression (5).

[Function and effect of conditional expression defining range of (dsi) / L]
Conditional expression (6) defines the range of the ratio between the distance dsi between the stop St and the imaging plane Km on the optical axis Z1 and the optical total length L.

  By configuring the imaging lens and the imaging device so as to satisfy the conditional expression (6), the imaging lens and the imaging device can be made compact.

  If the upper limit of conditional expression (6) is exceeded, the space between the first lens group G1 and the second lens group G2 is narrowed, so that higher-order spherical aberration occurs and the performance deteriorates. On the other hand, if the lower limit of conditional expression (6) is not reached, the optical total length L increases. If it is attempted to suppress the elongation of the optical total length L, as described above, the bulge of spherical aberration increases and performance degradation occurs.

  The operations and effects of the conditional expressions (6 ′) and (6 ″) are the same as those in the conditional expression (6).

  When the imaging lens 100 is applied to the imaging device 200, a cover glass, a low-pass filter, an infrared cut filter, or the like between the imaging lens 100 and the imaging element 210 is substantially used depending on the configuration of the imaging device 200. An optical element LL that does not have refractive power can be disposed. For example, when the imaging lens 100 is mounted on an in-vehicle camera and used as a night surveillance camera, light having a wavelength ranging from ultraviolet light to blue light is interposed between the imaging lens 100 and the imaging element 210. It is desirable to insert a filter that cuts.

  Further, instead of arranging a low-pass filter or various filters that cut a specific wavelength range between the imaging lens 100 and the imaging element 210, various filters are arranged between lenses constituting the imaging lens, A thin film having the same effect as various filters can be formed (coated) on the lens surface constituting the imaging lens.

  When the imaging lens 100 is applied to, for example, outdoor monitoring, it is required that the imaging lens 100 can be used in a wide temperature range from outside air in a cold region to the interior of a tropical summer car. In such a case, it is preferable that the material of all the lenses constituting each imaging lens is glass. In order to manufacture lenses at low cost, it is preferable that all lenses constituting each imaging lens are spherical lenses. However, when priority is given to optical performance over cost, an aspheric lens can be employed.

  Next, examples showing specific numerical data of the imaging lens according to the present invention will be described.

  Hereinafter, numerical data and the like of each of Examples 1 to 5 of the imaging lens of the present invention will be described together with reference to FIGS. 2 to 6 and FIGS. 7 to 11 and Tables 1 to 6. Note that the reference numerals in FIGS. 2 to 6 that are the same as the reference numerals in FIG. 1 indicate configurations corresponding to each other.

  The imaging lenses of Examples 1 to 5 are configured so as to satisfy all the conditional expressions. Further, all the lenses constituting the imaging lenses of Examples 1 to 5 are spherical lenses.

<Example 1>
FIG. 2 is a cross-sectional view illustrating a schematic configuration of the imaging lens of the first embodiment.

  Table 1 shows lens data of the imaging lens of Example 1. In the lens data shown in Table 1, the surface number i is the i-th (i = 1, 2, 3,...) Surface Si that sequentially increases toward the image side with the surface arranged closest to the object side as the first. Indicates the face number. The lens data in Table 1 are assigned surface numbers including the aperture stop St and the optical element LL having no power.

  The symbol Ri in Table 1 indicates the radius of curvature of the i-th (i = 1, 2, 3,...) Surface, and the symbol Di is the i (i = 1, 2, 3,...) Surface. And the surface interval on the optical axis Z1 between the i + 1th surface and the i + 1th surface. Symbols Ri and Di correspond to numbers corresponding to symbols Si (i = 1, 2, 3,...) Indicating lens surfaces, aperture stops, and the like.

  In addition, the symbol Ndj in Table 1 indicates the d-line (wavelength) of the j-th (j = 1, 2, 3,...) Optical element that sequentially increases toward the image side with the most optical element on the object side as the first. 587.6 nm), and νdj represents the Abbe number of the j-th optical element with respect to the d-line. In Table 1, the unit of the radius of curvature and the surface interval is mm, and the radius of curvature is positive when convex on the object side and negative when convex on the image side.

In addition, since the optical system as described above can maintain a predetermined performance even when the dimensions of optical elements such as lenses are proportionally enlarged or proportionally reduced, the entire lens data is proportionally enlarged or proportionally reduced. The imaging lens can also be an embodiment according to the present invention.

  FIG. 7 shows aberration diagrams of the imaging lens of Example 1. FIG. 7 shows aberration diagrams of spherical aberration, astigmatism, distortion (distortion aberration), and lateral chromatic aberration. The diagram indicated by symbol (a) represents spherical aberration, the diagram denoted by symbol (b) represents astigmatism, the diagram denoted by symbol (c) represents distortion, and the diagram denoted by symbol (d) represents lateral chromatic aberration. .

  In FIG. 7, various aberrations relating to light having wavelengths of d-line, F-line, and C-line are shown.

  Also, the solid line in the astigmatism diagram indicates the sagittal aberration, and the broken line indicates the tangential aberration. Further, F described in the upper part of the spherical aberration diagram means the F number, and ω described in the upper part of the other aberration diagrams means the half angle of view.

  Further, Table 6 shows values corresponding to the respective mathematical expressions in the conditional expressions for the imaging lenses of Examples 1 to 5. In addition, the value of the numerical formula described in each conditional expression can be calculated | required from the lens data etc. which are shown in Table 1.

  As can be seen from the lens data and the like, the imaging lens of Example 1 can be a bright and wide-angle and compact imaging lens in which various aberrations are well corrected.

  FIG. 2 showing the configuration of the imaging lens of the first embodiment, FIG. 7 showing the various aberrations, Table 1 showing the lens data, and how to read Table 6 relating to each conditional expression are also in Examples 2 to 5 described later. Since these are the same, explanations of Examples 2 to 5 described later are omitted.

<Example 2>
FIG. 3 is a cross-sectional view illustrating a schematic configuration of the imaging lens of the second embodiment.

  The imaging lens of Example 2 is configured to satisfy all the conditional expressions.

  FIG. 8 is a diagram showing various aberrations of the imaging lens of Example 2.

Table 2 below shows lens data of the imaging lens of Example 2.

<Example 3>
FIG. 4 is a cross-sectional view illustrating a schematic configuration of the imaging lens of the third embodiment.

  The imaging lens of Example 3 is configured to satisfy all the conditional expressions.

  FIG. 9 is a diagram illustrating various aberrations of the imaging lens of Example 3.

Table 3 below shows lens data of the imaging lens of Example 3.

<Example 4>
FIG. 5 is a cross-sectional view illustrating a schematic configuration of the imaging lens of the fourth embodiment.

  The imaging lens of Example 4 is configured to satisfy the above conditional expression.

  FIG. 10 is a diagram illustrating various aberrations of the imaging lens of Example 4.

Table 4 below shows lens data of the imaging lens of Example 4.

<Example 5>
FIG. 6 is a cross-sectional view illustrating a schematic configuration of the imaging lens of the fifth embodiment.

  The imaging lens of Example 5 is configured to satisfy all the conditional expressions.

  FIG. 11 is a diagram illustrating various aberrations of the imaging lens of Example 5.

Table 5 below shows lens data of the imaging lens of Example 5.

Table 6 below shows values related to the conditional expressions as described above.

  As can be seen from the above, the imaging lenses of Examples 1 to 5 can be a bright and wide-angle and compact imaging lens in which various aberrations are well corrected.

  FIG. 12 is a schematic configuration diagram of a surveillance camera as a specific example of the embodiment of the imaging apparatus of the present invention. A monitoring camera 200 shown in FIG. 12 includes an imaging lens 100 of the present invention disposed inside a substantially cylindrical lens barrel, and an imaging element 210 that captures an optical image of a subject formed by the imaging lens 100. I have. An optical image formed on the light receiving surface of the image sensor 210 through the imaging lens 100 is converted into an electric signal Gs and output from the monitoring camera 200.

  The present invention has been described with reference to the imaging lenses of the first to third embodiments, the imaging devices of the first to third embodiments, and Examples 1 to 5. It is not limited to an example, A various deformation | transformation is possible. For example, the values of the radius of curvature, the surface spacing, the refractive index, the Abbe number, etc. of each lens are not limited to the values shown in the above numerical examples, but can take other values.

  In addition, as a specific example of the embodiment of the imaging apparatus, an example in which the present invention is applied to a surveillance camera has been illustrated and described. However, the present invention is not limited to such an application. The present invention can also be applied to a video camera, an electronic still camera, a mobile terminal camera, an in-vehicle camera, a reading camera for the purpose of detecting a defect or identifying an individual.

Claims (23)

In order from the object side, a negative first lens group, a positive second lens group,
The first lens group comprises only a first lens that is a single biconcave lens;
The second lens group includes, in order from the object side, a cemented lens having a positive refractive power as a whole by cementing a second lens that is a positive lens and a third lens that is a negative lens in this order from the object side; Consists of an aperture, a fourth lens that is a positive lens, and a fifth lens that is a negative lens,
An imaging lens that satisfies the following conditional expressions (1a) and (2a) simultaneously:
0 <f23 / f <2.5 (1a)
0 <f45 / f <6 (2a)
However,
f23: the combined focal length of the second lens and the third lens f45: the combined focal length of the fourth lens and the fifth lens f: the focal length of the entire lens system The imaging lens according to claim 1, wherein the following conditional expression (1a ′) is satisfied.
0.6 <f23 / f <2 (1a ′) The imaging lens according to claim 1, wherein the following conditional expression (1a ″) is satisfied.
1 <f23 / f <1.8 (1a ″) The imaging lens according to claim 1, wherein the following conditional expression (2a ′) is satisfied.
0.5 <f45 / f <5.5 (2a ′) The imaging lens according to claim 1, wherein the following conditional expression (2a ″) is satisfied.
2 <f45 / f <5 (2a ″) In order from the object side, a negative first lens group, a positive second lens group,
The first lens group includes only a first lens which is a single negative lens,
The second lens group includes, in order from the object side, a cemented lens having a positive refractive power as a whole by cementing a second lens that is a positive lens and a third lens that is a negative lens in this order from the object side; Consists of an aperture, a fourth lens that is a positive lens, and a fifth lens that is a negative lens,
An imaging lens that satisfies the following conditional expressions (1b) and (2b) simultaneously:
0.9 <f23 / f <2.4 (1b)
2.8 <f45 / f <6 (2b)
However,
f23: the combined focal length of the second lens and the third lens f45: the combined focal length of the fourth lens and the fifth lens f: the focal length of the entire lens system The imaging lens according to claim 6, wherein the following conditional expression (1b ′) is satisfied.
1 <f23 / f <2 (1b ′) The imaging lens according to claim 6, wherein the following conditional expression (1b ″) is satisfied.
1.1 <f23 / f <1.6 (1b ″) The imaging lens according to claim 6, wherein the following conditional expression (2b ′) is satisfied.
2.9 <f45 / f <5 (2b ′) The imaging lens according to claim 6, wherein the following conditional expression (2b ″) is satisfied.
3 <f45 / f <4.2 (2b ″) In order from the object side, a negative first lens group, a positive second lens group,
The first lens group includes only a first lens which is a single negative lens,
The second lens group includes, in order from the object side, a cemented lens having a positive refractive power as a whole by cementing a second lens that is a positive lens and a third lens that is a negative lens in this order from the object side; It consists of a stop, a cemented lens having a positive refractive power as a whole by cementing a fourth lens as a positive lens and a fifth lens as a negative lens in this order from the object side,
An imaging lens satisfying the following conditional expression (3a):
0.9 <fg2 / f <1.8 (3a)
However,
fg2: focal length of the second lens unit f: focal length of the entire lens system The imaging lens according to claim 11, wherein the following conditional expression (3a ′) is satisfied.
1 <fg2 / f <1.6 (3a ′) The imaging lens according to claim 11, wherein the following conditional expression (3a ″) is satisfied.
1.05 <fg2 / f <1.4 (3a ″)   The imaging lens according to claim 6, wherein the first lens is a biconcave lens. The second lens is a biconvex lens;
The third lens is a negative lens having a concave surface facing the object side;
The fourth lens is a biconvex lens;
The imaging lens according to claim 6, wherein the fifth lens is a negative lens having a concave surface directed toward the object side.   The imaging lens according to claim 6, wherein the third lens has a meniscus shape.   The imaging lens according to claim 6, wherein the fifth lens has a meniscus shape.   18. The imaging lens according to claim 6, wherein the fourth lens and the fifth lens form a cemented lens having a positive refractive power as a whole joined together. . The imaging lens according to claim 1, wherein the following conditional expression (3b) is satisfied.
0.5 <fg2 / f <2.5 (3b)
However,
fg2: focal length of the second lens unit f: focal length of the entire lens system The imaging lens according to claim 1, wherein the following conditional expression (4) is satisfied.
-2 <f1 / fg2 <0 (4)
f1: Focal length of the first lens fg2: Focal length of the second lens group The imaging lens according to claim 1, wherein the following conditional expression (5) is satisfied.
1.5 <(dsi) / f <3.2 (5)
However,
dsi: Distance on the optical axis between the stop and the imaging surface (the back focus part is the air equivalent distance)
f: Focal length of the entire lens system The imaging lens according to any one of claims 1 to 21, wherein the following conditional expression (6) is satisfied.
0.42 <(dsi) / L <1 (6)
However,
L: Optical total length   An imaging apparatus comprising the imaging lens according to any one of claims 1 to 22.

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